2002 chevy 3500 6.5 van. Last year about this time my pmd went bad so I changed it. Thanks to you all. Now the van has stated bucking and hard start. I changed the pmd again (just in case), and the fuel filter. Van gives me a code p0251. Any ideas or suggestion. Just started the van and noticed that the check engine light goes on, off, on, off. does not stay light an then go off. hear a clicking each time the light goes on and off. Thanks Alex